No word from stuck NASA Mars rover Spirit

The odometer on the Mars rover Spirit has been stuck at 4.8 miles for more than 1 1/2 years and has been incommunicado since March.

This double dose of bad luck hangs over the scrappy spacecraft, which marks its seventh year on Mars on Monday.

NASA doesn't know if the Spirit is dead or alive, but it's diligently listening for any peep as the rover remains mired in a sand trap.

"There's a realistic possibility that Spirit may never wake up again," said Dave Lavery, Mars rovers program executive at NASA headquarters.

A pair of Mars orbiters has been making daily overhead passes listening for a signal from Spirit, which became stuck in April 2009 while driving backward. After several attempts to free it were unsuccessful, Spirit got new instructions to conduct science observations while mired in the sand.